1. Field of the Invention
The present invention relates to a data transmission and reception technique, and more particularly, to a method and a device for data transmission and reception for realizing a data delivery from a single data transmission device to a plurality of data reception devices as well as a simultaneous data delivery to a plurality of data reception devices economically.
2. Description of the Background Art
A conventional technique in a case of transmitting and receiving data using a communication channel is that, after a physical line is connected and a procedure to make a preparation for the data transmission and reception is carried out, the transparent one-to-one data communication is carried out while maintaining a logical connection state. Also, in a case of communications in the speech bandwidth as in a case of general subscriber telecommunications, the modulation and demodulation (modem) technique for converting digital data into analog signals in the speech bandwidth or vice versa is used. As the standard for this modulation and demodulation, V,21, V.22, V.22bis, V.32, V.32bis, V.34, etc. are defined for the data communications, but these standards are all for realizing the one-to-one bi-directional data communications.
However, the above described conventional scheme is not economical in a case of carrying out the data transmission and reception between one data transmission device and a plurality of data reception devices, because it requires as many devices (such as modems) as a total number of data transmitting and receiving pairs involved. In addition, when a plurality of reception requests are made simultaneously, there can be a problem in that the devices on the transmitting side may run out short so that it may not be possible to receive the requested data.